Genetic independence between traits separated by metamorphosis is widespread but varies with biological function

Why is metamorphosis so pervasive? Does it facilitate the independent (micro)evolution of quantitative traits in distinct life stages, similarly to how it enables some limbs and organs to develop at specific life stages? We tested this hypothesis by measuring the expression of 6400 genes in 41 Drosophila melanogaster inbred lines at larval and adult stages. Only 30% of the genes showed significant genetic correlations between larval and adult expression. By contrast, 46% of the traits showed some level of genetic independence between stages. Gene ontology terms enrichment revealed that across stages correlated traits were often involved in proteins synthesis, insecticide resistance and innate immunity, while a vast number of genes expression traits associated with energy metabolism were independent between life stages. We compared our results to a similar case: genetic constraints between males and females in gonochoric species (i.e. sexual antagonism). We expected selection for the separation between males and females to be higher than between juvenile and adult functions, as gonochorism is a more common strategy in the animal kingdom than metamorphosis. Surprisingly, we found that inter-stage constraints were lower than inter-sexual genetic constraints. Overall, our results show that metamorphosis enables a large part of the transcriptome to evolve independently at different life stages.

Microbiota acquisition and transmission in Drosophila flies

Understanding the ecological and evolutionary dynamics of host-microbiota associations notably involves exploring how members of the microbiota assemble and whether they are transmitted along host generations. Here, we investigate the larval acquisition of facultative bacterial and yeast symbionts of Drosophila melanogaster and Drosophila suzukii in ecologically realistic setups. Fly mothers and fruit were major sources of symbionts. Microorganisms associated with adult males also contributed to larval microbiota, mostly in D. melanogaster. Yeasts acquired at the larval stage maintained through metamorphosis, adult life, and were transmitted to offspring. All these observations varied widely among microbial strains, suggesting they have different transmission strategies among fruits and insects. Our approach shows microbiota members of insects can be acquired from a diversity of sources and highlights the compound nature of microbiotas. Such microbial transmission events along generations should favor the evolution of mutualistic interactions and enable microbiota-mediated local adaptation of the insect host.

Microbiota-mediated competition between Drosophila species

BACKGROUND

The influence of microbiota in ecological interactions, and in particular competition, is poorly known. We studied competition between two insect species, the invasive pest Drosophila suzukii and the model Drosophila melanogaster, whose larval ecological niches overlap in ripe, but not rotten, fruit.

RESULTS

We discovered D. suzukii females prevent costly interspecific larval competition by avoiding oviposition on substrates previously visited by D. melanogaster. More precisely, D. melanogaster association with gut bacteria of the genus Lactobacillus triggered D. suzukii avoidance. However, D. suzukii avoidance behavior is condition-dependent, and D. suzukii females that themselves carry D. melanogaster bacteria stop avoiding sites visited by D. melanogaster. The adaptive significance of avoiding cues from the competitor's microbiota was revealed by experimentally reproducing in-fruit larval competition: reduced survival of D. suzukii larvae only occurred if the competitor had its normal microbiota.

CONCLUSIONS

This study establishes microbiotas as potent mediators of interspecific competition and reveals a central role for context-dependent behaviors under bacterial influence. Video Abstract.

Influence of bacteria on the maintenance of a yeast during Drosophila melanogaster metamorphosis

Interactions between microorganisms associated with metazoan hosts are emerging as key features of symbiotic systems. Little is known about the role of such interactions on the maintenance of host-microorganism association throughout the host’s life cycle. We studied the influence of extracellular bacteria on the maintenance of a wild isolate of the yeast Saccharomyces cerevisiae through metamorphosis of the fly Drosophila melanogaster reared in fruit. Yeasts maintained through metamorphosis only when larvae were associated with extracellular bacteria isolated from D. melanogaster faeces. One of these isolates, an Enterobacteriaceae, favoured yeast maintenance during metamorphosis. Such bacterial influence on host-yeast association may have consequences for the ecology and evolution of insect-yeast-bacteria symbioses in the wild.

POS1417 DO SOCIAL FACTORS IMPACT ON BIOLOGICS COSTS IN RHEUMATOID ARTHRITIS? RESULTS FROM THE MOROCCAN RBSMR REGISTRY

Background:

Objectives:

The aim of this study was to estimate the annual direct cost of biologics in rheumatoid arthritis and to evaluate the impact of social factors on biological use and costs.

Methods:

Patients in the Moroccan register of biologicals (RBSMR) with available 1-year data were included. Variables related to socio-economic status, disease and biological were collected. Direct costs included prices of biologics, costs of infusions, and subcutaneous injections. Biological use and costs were compared based on social factors.

Results:

Our study included 197 patients (female sex of 86.8%, mean age of 52.3 ± 11 years). Patients were on one of the following therapies: Rituximab (n=132), Tocilizumab (n=37) or TNF-blockers (n=28). 44.2% of included patients have the RAMED medical assistance (health insurance scheme for the economically underprivileged). Illiteracy was noted in 45.7% of cases. Median one-year direct costs per patient were €1,665 [€1,472 - €9,879].

There was no statistically significant difference in costs between men and women (p>0.05), between illiterate and literate (p>0.05). There was a statistically significant difference in costs between patients with the RAMED medical assistance scheme and other health insurances (p<0.01).

Conclusion:

This study showed that Moroccan RA patients had equal access to biologics regardless of their gender or level of education. Indeed, the insurance system influence the costs of biologics. Accessibility of those expensive treatments in a developing country seems be explained by efforts of the Moroccan ministry of health who has allocated a substantial budget for biologic DMARDs for patients with RAMED in the tertiary structures in our country.

Disclosure of Interests:

None declared

AB0486 ONE-YEAR DIRECT COSTS OF BIOLOGICAL THERAPY IN ANKYLOSING SPONDYLITIS AND ITS PREDICTIVE FACTORS: DATA FROM THE MOROCCAN RBSMR REGISTRY

Background:

NA

Objectives:

To estimate the annual direct costs of biological therapies in Spondyloarthropathies (SpA) and to establish possible factors associated with those costs.

Methods:

The main data source was the Moroccan registry of biological therapies in rheumatic diseases (RBSMR). We included SpA patients with available 1-year data. Variables related to socioeconomic status, disease and biological therapy were collected. Differences in costs across groups were tested by Mann–Whitney and Kruskal–Wallis tests. Correlations analysis was performed in search of factors associated with high costs.

Results:

We included 89 SpA patients. The mean age was 40.6± 13.6 years, with male predominance 68.9 %. Patients received one of the following therapies: TNF-blockers (n =79), Biosimilar of TNF-blockers (n =8) and Il17-blockers (n =2). Median one-year biologic costs per patient were 9 569, 39 €. The total annual of biotherapies in AS patients was 851 675, 98 €.

Figure 1

Annual mean drug costs per treated patient (€: Euro)

The costs are presented in Euro using an exchange rate of (1 Moroccan Dirham = 0.091Euro).

TNF-blockers constituted 95 % of the total annual budget. Biosimilar of TNF-blockers and Il17-blockers represented 3 % and 2 % of this overall budget, respectively.

Although the costs were not significantly different in terms of gender or level of study, the insurance type significantly affected the cost estimation.

No correlation was found between the annual direct costs of biotherapies and body mass index nor with BASFI or BASDAI.

Conclusion:

In Morocco, a developing country, the annual direct costs of biological therapies are high in AS patients. Our results may contribute to the development of strategies for better governance of these costs.

Disclosure of Interests:

None declared.

AB0811 DIRECT COST OF BIOLOGICS IN RHEUMATOID ARTHRITIS PATIENTS IN A DEVELOPING COUNTRY: RESULTS FOR THE MOROCCAN RBSMR REGISTRY

Objectives:

The aim of this study was to calculate direct costs amount in rheumatoid arthritis (R.A) patients in the Moroccan register of biologicals RBSMR registry.

Methods:

Patients in the Moroccan register of biologicals RBSMR registry with available 1-year data were included. Variables related to socio-economic status, disease and biological therapy were collected. Direct costs included prices of biologics, costs of infusions, and subcutaneous injections. Biologic use and costs were compared.

Results:

197 patients data (female sex (86,8%), mean age (52,3± 11 years), illiteraty (45,7%)) were analyzed. The median annual direct costs per patient were €1,665 [€1,472 - €9,879]. For all patients, the mean annual direct costs per treated patient for each biological agent is presented in Figure 1.

The total annual direct costs of biological agents in the RBSMR registry were 978 494 €. Rituximab was given to 67% of patients and constituted 25.7% of the total annual budget. TNF-blockers and Tocilizumab were prescribed in 14.2% and 18.8% of cases and represented respectively 27.3% and 47% of this overall budget.

Conclusion:

This study presents a global overview of the direct costs of biological therapy associated with RA patients, taking as a source the Moroccan registry of biological therapies in rheumatic diseases. Those results show that overall cost of biological agents according to the Moroccan register is very high. There is a real need for development of strategies for better governance of those costs.

Disclosure of Interests:

None declared

Yeast facilitates the multiplication of Drosophila bacterial symbionts but has no effect on the form or parameters of Taylor's law

Interactions between microbial symbionts influence their demography and that of their hosts. Taylor’s power law (TL)–a well-established relationship between population size mean and variance across space and time–may help to unveil the factors and processes that determine symbiont multiplications. Recent studies suggest pervasive interactions between symbionts in Drosophila melanogaster. We used this system to investigate theoretical predictions regarding the effects of interspecific interactions on TL parameters. We assayed twenty natural strains of bacteria in the presence and absence of a strain of yeast using an ecologically realistic set-up with D. melanogaster larvae reared in natural fruit. Yeast presence led to a small increase in bacterial cell numbers; bacterial strain identity largely affected yeast multiplication. The spatial version of TL held among bacterial and yeast populations with slopes of 2. However, contrary to theoretical prediction, the facilitation of bacterial symbionts by yeast had no detectable effect on TL’s parameters. These results shed new light on the nature of D. melanogaster’s symbiosis with yeast and bacteria. They further reveal the complexity of investigating TL with microorganisms.

THU0642-HPR EVOLUTION OF THE PERCEPTIONS OF RA PATIENTS AFTER EDUCATION PATIENT SESSION TEACHING METHOTREXATE SELF-INJECTION A PROSPECTIVE PILOT STUDY

Background:

Methotrexate is a gold standard for treatment of RA. In our context, RA patients prefer to be injected by paramedics rather than self-injecting. This can be explained by patients’ bad perceptions of self-injection or lack of information. Appropriate self-injection education can therefore be an important element in overcoming these obstacles and improving disease self-management.

Objectives:

Compare the RA patients’ perceptions on methotrexate self-injection before and after a patient education session.

Methods:

Prospective pilot study that included 27 consecutive patients (81.5% female, mean age 44.4 years, illiteracy rate 40.7%) with RA (median duration of progression of 4 years, mean delay in referral for specialist of 6 months, median duration of methotrexate use of 1 year). The patients benefited from an individual patient education session to learn how to self-inject with methotrexate subcutaneously. The patient education session was supervised by a nurse and a rheumatologist with a control a week later. Perceptions of the reluctance to self-inject and the difficulties encountered by patients were assessed before the patient education session, after the 1st and 2nd self-injection of methotrexate using a 10 mm visual analog scale. Patients also reported their level of satisfaction (10 mm VAS) after the 1st and 2nd self-injection.

Results:

The mean duration of patient education session is 13 min.

Table I compares the evolution of the degrees of reluctance to self-injection, the difficulties encountered, and the satisfaction experienced by the patients.

Table 1.

Evolution of RA patients’ perceptions on the methotrexate self-injection. (N = 27)

BeforeAfter the 1stself-injectionAfter the 2end self-injectionpVAS reluctance (0-10mm)6,5 ± 3,62,2 ± 2,91,0 ± 2,3<0,0001VAS difficulty (0-10mm)7,5 ± 2,62,5 ± 2,71,0 ± 1,9<0,0001VAS satisfaction (0-10mm)-8,9 ± 1,89,5 ± 1,50,002

Conclusion:

This study suggests the effectiveness of a methotrexate self-injection patient education session in RA patients. It also highlights the value of patient education in rheumatologic care. A large-scale study is necessary to better interpret and complete these preliminary results from this pilot study.

Disclosure of Interests:

None declared

OP0089 EFFICACY OF CLOMIPRAMINE FOR CHRONIC LUMBAR RADICULAR PAIN A RANDOMIZED CLINICAL TRIAL

Background:

Lumbar radicular pain is the most common chronic neuropathic pain syndrome. Antidepressants are highly recommended for neuropathic pain, but there is no evidence for their efficacy.

Objectives:

The aim of this double-blind, randomised, placebo-controlled trial is to determine whether Clomipramine (an antidepressant) is more effective than placebo in reducing pain in individuals with resistant chronic lumbar radicular pain.

Methods:

A double-blind, randomized, clinical trial. Sixty-two patients with resistant chronic lumbar radicular pain were included. (The sample size was calculated on the assumption that clomipramine would reduce the incidence of lumbar radicular pain of 35%, compared with placebo, with a two-sided test, an alpha level of 0.05, and a power of 85%). Patients were randomly allocated to receive either Clomipramine by slow intravenous infusion for 10 days in a hospital setting with progressively increasing doses, 25 mg on the first day, 50 mg on the second day and 75 mg on the third day until the tenth day, or placebo (500 ml of physiological serum a day). For both groups, paracetamol is added intravenously at a dose of 3g per day for ten days, Parecoxib for 3 days and ten sessions of lumbar spine rehabilitation including analgesic massage, muscle strengthening and joint maintenance. At the exit, clomipramine was relayed with 25 mg per day orally until the 90th day for clomipramine group, and paracetamol was authorized in both groups, in case of severe pain. The primary outcome was pain intensity, measured at baseline, 5th day, 10th day and 90th day using VAS pain (10 mm). Secondary outcome included DN4-questionnaire, lumbar radicular discomfort (VAS 10 mm), pain-free perimeter of walking (min), disability assessed using the Roland Morris Disability questionnaire and severity of mood symptoms assessed using the Hospital Anxiety and Depression scale (HAD), measured on days 0, 5, 10 and 90.

Results:

31 patients were assigned to the clomipramine group and 31 to the placebo group. There were no differences between the groups in demographic characteristics. Treatment by Clomipramine had a significantly greater reduction in pain, discomfort and DN4 from the 5thday (p = 0.000, p = 0.001 and p = 0.004 respectively) than the placebo, with an improvement maintained until 90th day. There was a statistically significant improvement in pain-free walking distance and disability for the clomipramine group from the 10thday (p = 0.02 and 0.001 respectively) and that maintained until 90thday. However, there was no significant improvement in HAD between the 2 groups. (p ≥ 0.1).

Conclusion:

This double-blind, randomized, clinical trial shows that clomipramine is quickly effective and maintained over time in the management of resistant chronic lumbar radicular pain. It can therefore be part of the therapeutic arsenal in this sense.

Disclosure of Interests:

None declared

FRI0620-HPR THE EFFECT OF THERMOFORMABLE FOOT ORTHOSES ON WALKING IN RHEUMATOID ARTHRITIS PATIENTS: PRELIMINARY RESULTS FROM AN OPEN CLINICAL TRIAL

Background:

Foot pain is common in rheumatoid arthritis and appears to persist despite modern day medical management.

Objectives:

To evaluate the impact of thermoformable foot orthoses on walking in rheumatoid arthritis (RA) patients.

Methods:

This is a open clinical trial, that included 14 consecutive patients (85,7% female, mean age 54,8 ± 10 years) with RA (median duration of progression of 9 [5-12] years), the average DAS28 was 2,7+/-1,2 and the functional impact objectified by the Health Assessment Questionnaire (HAQ) was on average 0.9 ± 0.7.

The foot problem was bilateral in 100% and inaugural in 85.7% of the cases.

The 14 rheumatoid subjects were examined and appropriate foot orthoses were prescribed according to each patient’s needs. All the patients were evaluated at baseline and 8 weeks after use of orthoses. Gait pain, difficulty walking and the 10 Meter Walk test were noted at each appointment.

We used dynamic baropodometric analysis to assess postural evaluation. We calculated the lateral-medial index of each foot before and after the use of orthoses.

Table 1.

Assessment of walking before and after the use of orthoses

Before orthosesAfter orthosespPain when walking*(EVA 0-10)5 [3-5,2]0 [0-2]0,002Difficulty walking* (0-10)- In house4 [3-5,2]2 [0-2]0,002- Outside6 [4,7-7]2 [1,5-2,5]0,0210 Meter Walk test**(Normal comfortable speed)- Nomber of steps18,64 ± 3,716,9 ± 50,2- Duration (sec)11,9 ± 4,611,8 ± 5,20,9- Walking speed (m/min)56,4 ±17,758,6 ± 20,30,6latero-medial (L/M) index**- L/M index of the right foot1,18 ± 0,171,23 ± 0,230,1- L/M index of the left foot1,25 ± 0,171,26 ± 0,190,9

*median and quartile

**average and standard deviation

p significant if< 0,05

Results:

A significant decrease in walking pain (p = 0.002) and difficulty walking (p = 0.02) was found with the use of orthoses. The variations in 10 meter walk test and dynamic baropodometric parameters were not significant (p>0,05).

There were no significant correlations between pain and difficulty walking, the progression of RA, the duration of foot damage and the functional impact measured by the HAQ.

Conclusion:

Thermoformable foot orthoses significantly reduced pain and difficulty walking. The absence of factors associated with pain and difficulty walking could possibly be related to the small sample size.

Disclosure of Interests:

None declared

THU0641-HPR ILLITERACY IS NOT AN OBSTACLE FOR ASSIMILATION OF A PATIENT EDUCATION SESSION ON METHOTREXATE SELF-INJECTION IN RA PATIENTS A PROSPECTIVE PILOT STUDY

Background:

Patient education for RA patients has been shown to improve adherence and self-management of this chronic disease.

Objectives:

To assess the impact of illiteracy on assimilation of a patient education session on methotrexate self-injection in RA patients.

Methods:

Prospective pilot study that included 27 consecutive patients (81.5% female, mean age 44.4 years, illiteracy rate 40.7%) with RA (median duration of progression of 4 years, mean delay in referral for specialist of 6 months, median duration of methotrexate use of 1 year). The patients benefited from an individual patient education session to learn how to self-inject with methotrexate subcutaneously. The patient education session was supervised by a nurse and a rheumatologist. A 10-question dichotomous questionnaire was then administered to patients to assess the level of uptake of messages passed during the patient education session. The prevalence of correct answers was compared between illiterate and non-illiterate patients.

Results:

The mean duration of patient education session is 13 min.

Table I illustrates the results of the correct responses prevalence and the comparison of correct response rates between illiterate and non-illiterate patients.

Table 1.

Prevalence of correct responses and comparison of correct response rates between illiterate and non-illiterate patients.

QuestionsN=27IlliteratePYes (N=11)No (N=16)1.Do I always have to self-inject on the same day of the week? (%)96,390,9100NS2.Should Methotrexate be protected from light and away from children? (%)96,310093,7NS3.Can I self-inject anywhere on my thigh and belly 5 cm from the navel? (%)85,210075NS4.Is it important to change the injection sites? (%)70,472,768,75NS5.Do I need to pinch the skin before self-injection? (%)92,610087,5NS6.Can I always use the same needle for each injection? (%)81,590,975NS7.Do I have to wear gloves to inject Methotrexate? (%)81,590,975NS8.Do I have to apply an antiseptic product (alcohol, Betadine) to the injection site before self-injecting? (%)88,990,987,5NS9.Can I use the rest of the MTX ampoule for the next injection? (%)74,181,868,7NS10.Do I tell my doctor if I have side effects? (%)100100100NS

Conclusion:

This study suggests that illiteracy does not affect the assimilation of information given during a patient education session. These preliminary results should encourage the development of patient education programs in our context where illiteracy rate is high.

Disclosure of Interests:

None declared

AB1285-HPR ACCELEROMETRIC ASSESSMENT OF PHYSICAL PERFORMANCE DURING THE SIT-TO-STAND TEST IN PATIENTS WITH KNEE OSTEOARTHRITIS

Background:

Knee osteoarthritis is a major public health issue that causes chronic pain and functional limitation.

Objectives:

This study aims to evaluate physical performance in knee osteoarthritis by clinical tests and accelerometer measurements, and investigate the relationship between physical perfomance alteration and clinical parameters.

Methods:

This is a cross-sectional study, included 40 patients with knee osteoarthritis (100% female, average age 57.6 ± 5.2 years, median evolution time was 36 [24, 69] months, overweight in 82.5% of patients). Clinical evaluation performed with the visual analog scale (VAS), Western Ontario and McMaster Osteoarthritis Index (WOMAC), Lequesne score, Get up and Go (GUG) and Timed up and Go (TUG) tests. The percentage of fat mass was measured using impedencemetry.

All subjects were instructed to perform sit-to-stand transfers during 30 secondes. We measured the speed, strength and muscular power of the lower limbs during this test using the Myotest PRO® accelerometer.

A correlation analysis was performed in search of factors associated with physical performance alteration.

Results:

The median speed during the sit-to-stand test was 4.3 [3.1-6.2] cm / sec. The median muscular strength and power during this test were 15.2 [13.6-17.7] Nm / kg and 14.5 [9.9-21.7] W / kg respectively.

Body mass index (BMI) correlated negatively with the 3 parameters of physivcal performance mesured by the Myotest PRO® accelerometer (speed, strength and muscle power) during the sit-to-stand test (p<0,05). There was no correlation between those measured parameters of physical performance, pain and functional indices of knee osteoarthritis.

Conclusion:

Our pilot study assessed the physical performance of the lower limbs in knee osteoarthritis patients, by measuring the speed, strength and muscle power during the the sit-to-stand test. It suggests an association between obesity and physical performance alteration in knee osteoarthritis patients.

Disclosure of Interests:

None declared

Do traits separated by metamorphosis evolve independently? Concepts and methods

Despite the ubiquity of complex life cycles, we know little of the evolutionary constraints exerted by metamorphosis. Here, we present pitfalls and methods to answer whether animals with a complex life cycle can independently adapt to the environments encountered at each life stage, with a specific focus on the microevolution of quantitative characters. We first discuss challenges associated with study traits and populations. We further emphasize the benefits of using a combination of approaches. We then develop how multivariate methods can limit several issues by revealing genetic patterns that are invisible when only considering trait-by-trait genetic correlations. Finally, we detail how Lande's work on sexual dimorphism can be applied in measuring G matrices across life stages. The methods and tools described here will contribute towards building a predictive framework for trait evolution across life stages.

Performance of Metarhizium anisopliae-treated foam in combination with Phytoseiulus longipes Evans against Tetranychus evansi Baker & Pritchard (Acari: Tetranychidae)

BACKGROUND

Tetranychus evansi (Te) is an exotic pest of solanaceous crops in Africa. The predatory mite Phytoseiulus longipes (Pl) and the fungus Metarhizium anisopliae (Ma) are potential biocontrol agents of Te. The present study investigated the efficacy of fungus-treated foam placed above or below the third Te-infested tomato leaf. The persistence of fungus-treated foam and the performance of Pl with and without fungus-treated foam were evaluated.

RESULTS

The fungus-treated foam was effective when Te infestation was below the third tomato leaf as no damage was recorded on any of the upper tomato leaves up to 30 days post-treatment. However, in the control treatments, the infestation increased considerably from 9 ± 0.3% to 100 ± 0% (mean ± standard error) at 15 days post-treatment. The reuse of the fungus-treated foam at 15, 30 and 45 days post-treatment resulted in 19 ± 1.4%, 25 ± 1.2% and 54 ± 2.1%, respectively, infestation by Te. The fungus-treated foam and Pl alone were efficient, but there was no benefit to combining them for use against Te.

CONCLUSION

The fungus-treated foam is an effective method to optimise the use of Ma in screenhouse conditions. These two control agents could be integrated in an integrated pest management strategy for crop protection. However, these results need to be confirmed in large field trials. © 2018 Society of Chemical Industry.

The virome of Drosophila suzukii, an invasive pest of soft fruit

Drosophila suzukii (Matsumura) is one of the most damaging and costly pests to invade temperate horticultural regions in recent history. Conventional control of this pest is challenging, and an environmentally benign microbial biopesticide is highly desirable. A thorough exploration of the pathogens infecting this pest is not only the first step on the road to the development of an effective biopesticide, but also provides a valuable comparative dataset for the study of viruses in the model family Drosophilidae. Here we use a metatransciptomic approach to identify viruses infecting this fly in both its native (Japanese) and invasive (British and French) ranges. We describe eighteen new RNA viruses, including members of the Picornavirales, Mononegavirales, Bunyavirales, Chuviruses, Nodaviridae, Tombusviridae, Reoviridae, and Nidovirales, and discuss their phylogenetic relationships with previously known viruses. We also detect 18 previously described viruses of other Drosophila species that appear to be associated with D. suzukii in the wild.

Comparison of cauliflower-insect-fungus interactions and pesticides for cabbage root fly control

Cabbage root fly (Delia radicum L.) control represents a major challenge in brassica production, therefore different management strategies for its control were tested in conventionally managed open field cauliflower production. Strategies included treatments with low-risk methods such as nitrogen lime, the insecticide spinosad and the Beauveria bassiana ATCC 74040-based biopesticide Naturalis. Their effects were compared with treatments based on nonformulated fungal species Metarhizium brunneum, B. bassiana, Clonostachys solani, Trichoderma atroviride, T. koningiopsis, and T. gamsii and commercial insecticides λ-cyhalothrin and thiamethoxam. Spinosad and thiamethoxam were pipetted to individual plants before transplanting; λ-cyhalothrin was sprayed after transplanting; nitrogen lime was applied at first hoeing. Nonformulated fungi were delivered onto cauliflower plantlets' roots as a single pretransplantation inoculation. The cabbage root fly population dynamics exhibited a strong spatiotemporal variation. The lowest number of cabbage root fly pupae recovered from cauliflower roots in the field experiments was recorded in plants treated with spinosad (significant reduction), followed by Naturalis and one of the tested M. brunneum strains (nonsignificant reduction). Significantly more pupae were counted in the nitrogen lime treatment. The field experiments showed that a single drench of cauliflower plantlets with spinosad offered consistent and enduring cabbage root fly control. Naturalis and nonformulated fungal isolates did not decrease cabbage root fly pressure significantly, apparently due to lack of statistical power. The implications of the substantial intra- and inter-annual pest pressure variation and the benefits of using single plant treatments are discussed, and recommendations for improvement of rhizosphere-competence utilizing biological control strategies provided.

Deciphering the Routes of invasion of Drosophila suzukii by Means of ABC Random Forest

Deciphering invasion routes from molecular data is crucial to understanding biological invasions, including identifying bottlenecks in population size and admixture among distinct populations. Here, we unravel the invasion routes of the invasive pest Drosophila suzukii using a multi-locus microsatellite dataset (25 loci on 23 worldwide sampling locations). To do this, we use approximate Bayesian computation (ABC), which has improved the reconstruction of invasion routes, but can be computationally expensive. We use our study to illustrate the use of a new, more efficient, ABC method, ABC random forest (ABC-RF) and compare it to a standard ABC method (ABC-LDA). We find that Japan emerges as the most probable source of the earliest recorded invasion into Hawaii. Southeast China and Hawaii together are the most probable sources of populations in western North America, which then in turn served as sources for those in eastern North America. European populations are genetically more homogeneous than North American populations, and their most probable source is northeast China, with evidence of limited gene flow from the eastern US as well. All introduced populations passed through bottlenecks, and analyses reveal five distinct admixture events. These findings can inform hypotheses concerning how this species evolved between different and independent source and invasive populations. Methodological comparisons indicate that ABC-RF and ABC-LDA show concordant results if ABC-LDA is based on a large number of simulated datasets but that ABC-RF out-performs ABC-LDA when using a comparable and more manageable number of simulated datasets, especially when analyzing complex introduction scenarios.

Stable Polycomb-dependent transgenerational inheritance of chromatin states in Drosophila

Transgenerational Epigenetic Inheritance (TEI) studies the transmission of alternative functional states through multiple generations in the presence of the same genomic DNA sequence. Very little is known on the principles and the molecular mechanisms governing this type of inheritance. Here, by transiently enhancing 3D chromatin interactions, we established stable and isogenic Drosophila epilines that carry alternative epialleles, defined by differential levels of the Polycomb-dependent H3K27me3 mark. Once established, epialleles can be dominantly transmitted to naïve flies and induce paramutation. Importantly, epilines can be reset to a naïve state by disrupting chromatin interactions. Finally, we show that environmental changes can modulate the expressivity of the epialleles and we extend our paradigm to naturally occurring phenotypes. Our work sheds light on how nuclear organization and Polycomb group proteins contribute to epigenetically inheritable phenotypic variability.

Invasive Drosophila suzukii facilitates Drosophila melanogaster infestation and sour rot outbreaks in the vineyards

How do invasive pests affect interactions between members of pre-existing agrosystems? The invasive pest Drosophila suzukii is suspected to be involved in the aetiology of sour rot, a grapevine disease that otherwise develops following Drosophila melanogaster infestation of wounded berries. We combined field observations with laboratory assays to disentangle the relative roles of both Drosophila in disease development. We observed the emergence of numerous D. suzukii, but no D. melanogaster flies, from bunches that started showing mild sour rot symptoms days after field collection. However, bunches that already showed severe rot symptoms in the field mostly contained D. melanogaster. In the laboratory, oviposition by D. suzukii triggered sour rot development. An independent assay showed the disease increased grape attractiveness to ovipositing D. melanogaster females. Our results suggest that in invaded vineyards, D. suzukii facilitates D. melanogaster infestation and, consequently, favours sour rot outbreaks. Rather than competing with close species, the invader subsequently permits their reproduction in otherwise non-accessible resources and may cause more frequent, or more extensive, disease outbreaks.

Invasive Drosophila suzukii facilitates Drosophila melanogaster infestation and sour rot outbreaks in the vineyards

How do invasive pests affect interactions between members of pre-existing agrosystems? The invasive pest Drosophila suzukii is suspected to be involved in the aetiology of sour rot, a grapevine disease that otherwise develops following Drosophila melanogaster infestation of wounded berries. We combined field observations with laboratory assays to disentangle the relative roles of both Drosophila in disease development. We observed the emergence of numerous D. suzukii, but no D. melanogaster flies, from bunches that started showing mild sour rot symptoms days after field collection. However, bunches that already showed severe rot symptoms in the field mostly contained D. melanogaster. In the laboratory, oviposition by D. suzukii triggered sour rot development. An independent assay showed the disease increased grape attractiveness to ovipositing D. melanogaster females. Our results suggest that in invaded vineyards, D. suzukii facilitates D. melanogaster infestation and, consequently, favours sour rot outbreaks. Rather than competing with close species, the invader subsequently permits their reproduction in otherwise non-accessible resources and may cause more frequent, or more extensive, disease outbreaks.

Isolation, characterization and PCR multiplexing of microsatellite loci for a mite crop pest, Tetranychus urticae (Acari: Tetranychidae)

Background

Tetranychus urticae is a highly polyphagous species with a cosmopolitan distribution that has the status of pest in more than 100 economically significant crops all over the world. Despite a number of previous efforts to isolate genetic markers, only a reduced set of microsatellite loci has been published. Taking advantage of the whole genome sequence of T. urticae that recently became available; we isolated and characterized a new set of microsatellite loci and tested the level of polymorphism across populations originating from a wide geographical area.

Results

A total of 42 microsatellite sequences widespread in the T. urticae genome were identified, the exact position in the genome recorded, and PCR amplification of microsatellite loci tested with primers defined here. Fourteen loci showed unambiguous genotype patterns and were further characterized. Three multiplex polymerase chain reaction sets were optimized in order to genotype a total of 24 polymorphic loci, including 10 previously published Tetranychus-specific loci. The microsatellite kits successfully amplified 686 individuals from 60 field populations for which we assessed the level of genetic diversity. The number of alleles per locus ranged from 3 to 16 and the expected heterozygosity values ranged from 0.12 to 0.81. Most of the loci displayed a significant excess of homozygous and did not model the Hardy–Weinberg equilibrium. This can be explained by the arrhenotokous mode of reproduction of T. urticae.

Conclusions

These primers represent a valuable resource for robust studies on the genetic structure, dispersal and population biology of T. urticae, that can be used in managing this destructive agricultural pest.

Dispersal behavior of Tetranychus evansi and T. urticae on tomato at several spatial scales and densities: implications for integrated pest management

Studying distribution is necessary to understand and manage the dynamics of species with spatially structured populations. Here we studied the distribution in Tetranychus evansi and T. urticae, two mite pests of tomato, in the scope of evaluating factors that can influence the effectiveness of Integrated Pest Management strategies. We found greater positive density-dependent distribution with T. evansi than T. urticae when assayed on single, detached tomato leaves. Indeed, T. evansi distribution among leaflets increased with initial population density while it was high even at low T. urticae densities. Intensity and rate of damage to whole plants was higher with T. evansi than T. urticae. We further studied the circadian migration of T. evansi within plant. When T. evansi density was high the distribution behavior peaked between 8 am and 3 pm and between 8 pm and 3 am local time of Kenya. Over 24 h the total number of mites ascending and descending was always similar and close to the total population size. The gregarious behavior of T. evansi combined with its rapid population growth rate, may explain why few tomato plants can be severely damaged by T. evansi and how suddenly all the crop can be highly infested. However the localisation and elimination of the first infested plants damaged by T. evansi could reduce the risk of outbreaks in the entire crop. These findings suggest also that an acaricide treated net placed on the first infested plants could be very effective to control T. evansi. Moreover circadian migration would therefore accentuate the efficiency of an acaricide treated net covering the infested plants.

Phenotypic plasticity in evolutionary rescue experiments

Population persistence in a new and stressful environment can be influenced by the plastic phenotypic responses of individuals to this environment, and by the genetic evolution of plasticity itself. This process has recently been investigated theoretically, but testing the quantitative predictions in the wild is challenging because (i) there are usually not enough population replicates to deal with the stochasticity of the evolutionary process, (ii) environmental conditions are not controlled, and (iii) measuring selection and the inheritance of traits affecting fitness is difficult in natural populations. As an alternative, predictions from theory can be tested in the laboratory with controlled experiments. To illustrate the feasibility of this approach, we briefly review the literature on the experimental evolution of plasticity, and on evolutionary rescue in the laboratory, paying particular attention to differences and similarities between microbes and multicellular eukaryotes. We then highlight a set of questions that could be addressed using this framework, which would enable testing the robustness of theoretical predictions, and provide new insights into areas that have received little theoretical attention to date.

Quorum sensing and density-dependent dispersal in an aquatic model system

Many organisms use cues to decide whether to disperse or not, especially those related to the composition of their environment. Dispersal hence sometimes depends on population density, which can be important for the dynamics and evolution of sub-divided populations. But very little is known about the factors that organisms use to inform their dispersal decision. We investigated the cues underlying density-dependent dispersal in inter-connected microcosms of the freshwater protozoan Paramecium caudatum. In two experiments, we manipulated (i) the number of cells per microcosm and (ii) the origin of their culture medium (supernatant from high- or low-density populations). We found a negative relationship between population density and rates of dispersal, suggesting the use of physical cues. There was no significant effect of culture medium origin on dispersal and thus no support for chemical cues usage. These results suggest that the perception of density – and as a result, the decision to disperse – in this organism can be based on physical factors. This type of quorum sensing may be an adaptation optimizing small scale monitoring of the environment and swarm formation in open water.

Genetic influence on disease spread following arrival of infected carriers

Epidemiology in host meta-populations depends on parasite ability to disperse between, establish and persist in distinct sub-populations of hosts. We studied the genetic factors determining the short-term establishment, and long-term maintenance, of pathogens introduced by infected hosts (i.e. carriers) into recipient populations. We used experimental populations of the freshwater ciliate Paramecium caudatum and its bacterial parasite Holospora undulata. Parasite short-term spread (approximately one horizontal transmission cycle) was affected mainly by carrier genotype, and its interactions with parasite and recipient genotypes. By contrast, parasite longer term spread (2-3 horizontal transmission cycles) was mostly determined by parasite isolate. Importantly, measures of parasite short-term success (reproductive number, R) were not good predictors for longer term prevalence, probably because of the specific interactions between host and parasite genotypes. Analogous to variation in vectorial capacity and super-spreader occurrence, two crucial components of epidemiology, we show that carrier genotype can also affect disease spread within meta-populations.

Taylor's Law holds in experimental bacterial populations but competition does not influence the slope

Populations vary in time and in space, and temporal variation may differ from spatial variation. Yet, in the past half century, field data have confirmed both the temporal and spatial forms of Taylor's power Law, a linear relationship between log(variance) and log(mean) of population size. Recent theory predicted that competitive species interactions should reduce the slope of the temporal version of Taylor's Law. We tested whether this prediction applied to the spatial version of Taylor's Law using simple, well-controlled laboratory populations of two species of bacteria that were cultured either separately or together for 24 h in media of widely varying nutrient richness. Experimentally, the spatial form of Taylor's Law with a slope of 2 held for these simple bacterial communities, but competitive interactions between the two species did not reduce the spatial Taylor's Law slope. These results contribute to the widespread usefulness of Taylor's Law in population ecology, epidemiology and pest control.

Adaptation of Paramecium caudatum to variable conditions of temperature stress

The environment is rarely constant and organisms are exposed to spatial and temporal variation that will impact life-histories. It is important to understand how such variation affects the adaptation of organisms to their local environment. We compare the adaptation of populations of the ciliate Paramecium caudatum exposed to constant (23 °C or 35 °C) and temporally variable temperature environments (random daily fluctuations between 23 °C or 35 °C). Consistent with theory, our experiment shows the evolution of specialists when evolution proceeds in constant environments and generalists when the environment is temporally variable. In addition, we demonstrate costs for specialists of being locally adapted through reduced fitness in novel environments. Conversely, we do not find any costs for generalists, as all populations from variable environments had equal or superior performance to specialists in their own environment. The lack of a cost for generalists is emphasised by the presence of a super generalist that has the highest performance at both assay temperatures.

Temporal variation in temperature determines disease spread and maintenance in Paramecium microcosm populations

The environment is rarely constant and organisms are exposed to temporal and spatial variations that impact their life histories and inter-species interactions. It is important to understand how such variations affect epidemiological dynamics in host-parasite systems. We explored effects of temporal variation in temperature on experimental microcosm populations of the ciliate Paramecium caudatum and its bacterial parasite Holospora undulata. Infected and uninfected populations of two P. caudatum genotypes were created and four constant temperature treatments (26°C, 28°C, 30°C and 32°C) compared with four variable treatments with the same mean temperatures. Variable temperature treatments were achieved by alternating populations between permissive (23°C) and restrictive (35°C) conditions daily over 30 days. Variable conditions and high temperatures caused greater declines in Paramecium populations, greater fluctuations in population size and higher incidence of extinction. The additional effect of parasite infection was additive and enhanced the negative effects of the variable environment and higher temperatures by up to 50 per cent. The variable environment and high temperatures also caused a decrease in parasite prevalence (up to 40%) and an increase in extinction (absence of detection) (up to 30%). The host genotypes responded similarly to the different environmental stresses and their effect on parasite traits were generally in the same direction. This work provides, to our knowledge, the first experimental demonstration that epidemiological dynamics are influenced by environmental variation. We also emphasize the need to consider environmental variance, as well as means, when trying to understand, or predict population dynamics or range.

Potential for evolutionary coupling and decoupling of larval and adult immune gene expression

Almost all studies of the immune system of animals with metamorphosis have focused on either larval or on adult immunity, implicitly assuming that these traits are either perfectly correlated or evolutionarily independent. In this study, we use 80 crosses among 21 Drosophila melanogaster lines to investigate the degree and constancy of genetic correlation in immune system activity between larvae and adults. The constitutive transcription of Diptericin, a gene encoding a defensive antimicrobial peptide, was controlled by the same genetic factors in larvae and adults, with variation in expression determined exclusively by nonadditive genetic effects. This contrasted with another peptide-encoding gene, Drosomycin, in which larval transcription was highly variable and determined by additive effects but adult transcription genetically invariant. We found no evidence for a fitness cost to the transcription of these genes in our study. The shared genetic control of larval and adult Diptericin transcription stands in contrast to predictions of the adaptive decoupling hypothesis, which states that distinct life-stages should permit the independent evolution of larval and adult phenotypes. Importantly, genetic correlations between larval and adult immunities imply that parasite pressure on one life-stage can drive the evolution of immunity (and resistance) in the other life-stage.

Parasitic infection reduces dispersal of ciliate host

Parasitic infection can modify host mobility and consequently their dispersal capacity. We experimentally investigated this idea using the ciliate Paramecium caudatum and its bacterial parasite Holospora undulata. We compared the short-distance dispersal of infected and uninfected populations in interconnected microcosms. Infection reduced the proportion of hosts dispersing, with levels differing among host clones. Host populations with higher densities showed lower dispersal, possibly owing to social aggregation behaviour. Parasite isolates that depleted host populations most had the lowest impact on host dispersal. Parasite-induced modification of dispersal may have consequences for the spatial distribution of disease, host and parasite genetic population structure, and coevolution.

How can your parasites become your allies?

Although parasitic infection is usually detrimental, it can be beneficial to the host in some situations. Parasites could help their host by providing a new function or modifying one of the host's life-history traits. We argue that the evolution towards a lasting mutualistic relationship would be more likely when parasites endow hosts with new abilities rather than alter a trait because hosts are less likely to evolve a new capability on their own than adjust their life history by microevolutionary steps. Furthermore, we underline how evolved dependence--the host's loss of ability to live alone owing to a long history of evolution in the presence of its parasites--has shaped contemporary mutualistic relationships.

Different transmission strategies of a parasite in male and female hosts

We investigated whether a parasite with two routes of transmission responds to the different transmission opportunities offered by male and female hosts by using different transmission strategies in the two sexes. The parasite Ascogregarina culicis, which infects the mosquito Aedes aegypti, can be transmitted as its host's pupa transforms into an adult or when a female lays its eggs. As the latter transmission route is missing in males, we expected, and found, that the parasite releases a greater proportion of its infectious forms during emergence when it is within a male than when it infects a female. The transmission route, which influences the parasite's dispersal and the evolution of its virulence, was also affected by the dose of infection and the parasite's previous transmission route. Our results emphasize the complexity underlying the development of parasites and show their ability to tune their strategy to their environment.

Condition-dependent effects of corticosterone on a carotenoid-based begging signal in house sparrows

Begging is a complex display involving a variety of different visual and auditory signals. Parents are thought to use these signals to adjust their investment in food provisioning. The mechanisms that ensure the honesty of begging displays as indicators of need have been recently investigated. It has been shown that levels of corticosterone (Cort), the hormone released during the stress response, increase during food shortage and are associated with an increased begging rate. In a recent study in house sparrows, although exogenous Cort increased begging rate, parents did not accordingly adjust their provisioning rate. Here, we tested the hypothesis that Cort might affect the expression of other components of begging displays, such as flange color (a carotenoid-based trait). We experimentally increased levels of circulating Cort and investigated the effects of the treatment on (1) the flange coloration of the nestlings, (2) the behavioral response and (3) the parental allocation of food and (4) nestling condition and cell-mediated immune response. We found that Cort affected flange coloration in a condition-dependent way. Cort-injected nestlings had less yellow flanges than controls only when in poor body condition. Parental feeding rate was also affected by the Cort treatment in interaction with flange color. Feeding rate of Cort-injected nestlings was negatively and significantly correlated with flange color (nestlings with yellower flanges receiving more food), whereas feeding rate and flange color were not correlated in control chicks. We also found that nestlings injected with Cort showed a weaker immune response than controls. These results suggest that, indeed, Cort has the potential to affect multiple components of the begging display. As Cort levels naturally raise during fasting, parents have to take into account these multiple components to take a decision as to optimally share their investment among competing nestlings.

Coevolutionary interactions between host and parasite genotypes

More than 20 years after Dawkins introduced the concept of "extended phenotype" (i.e. phenotypes of hosts and parasites result from interactions between the two genomes) and although this idea has now reached contemporary textbooks of evolutionary biology, most studies of the evolution of host-parasite systems still focus solely on either the host or the parasite, neglecting the role of the other partner. It is important to consider that host and parasite genotypes share control of the epidemiological parameters of their relationship. Moreover, not only the traits of the infection but also the genetic correlations among these and other traits that determine fitness might be controlled by interactions between host and parasite genotypes.